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-   -   Fuel pump short? 94FD (https://www.rx7club.com/new-member-rx-7-technical-256/fuel-pump-short-94fd-1123354/)

topheRx7 02-12-18 09:16 AM

Fuel pump short? 94FD
 
So after having my battery die(brand new red top) from infrequent driving (1-2weeks) i had starting issues. Basically even after a full charge on the battery my fuel pump was not coming on. It’s a Denso Supra FP with less than 2000 miles. This got me looking around the FP relay for a short and sure enough when I put a test light to the 4 areas the relay would make contact I get a light on the two sides that should light up but also a light on one of the two that I believe should not is this correct?. The line in question is a white wire with a red stripe about 3x thicker than the majority of the wires in the harness. Iv seen some post about bypassing the relay but wasn’t sure if it’s was the best solution for the problem. Any suggestions or help would be appreciated as iv chased the wire as well as I could with no luck finding the issue. The test light will show a short even with the pump disconnected as well as just about every fuse I could find to pull and that’s with the BTN fuse pulled as I know that fuse always draws a current for the CPU.

liquidusculade 02-21-18 09:46 AM

I had a starting issue when i first bought my fd. The engine did not run, and had been sitting for at least a year, so in my troubleshooting i discovered the injectors were not spraying fuel, then found i wasnt even getting pressure. I troubleshot the relays, the resistor, and all the wiring, I eventually troubleshot it down to the ecu. I thought it was an ecu issue but decided to check the fuses first. Fuel pump fuse was fine, all the fuses were fine, but after pulling out the room fuse, and reinserting the room fuse everything worked like it should. I guess there was some oxidation that built up on the fuses and was causing issues. My car is a 93 r1, not sure how different your wiring is from mine. Do you have the workshop manual?

topheRx7 02-21-18 11:49 AM

I do however of course out of all the books I have I cannot seem to find the one with the wiring diagram. The main focus I have for thinking it is a electrical issue is that my battery started dying the same time this issue came up and I’m getting a test light to light up on the negative side of my fuel pump relay terminal when the relay is pulled out. Is the room fuse the one that keeps power to the cpu when the car is off? Thanks for the reply.

rxtasy3 02-21-18 12:17 PM

have u tried looking here:

Foxed.ca - Mazda RX-7 Manuals

liquidusculade 03-02-18 06:46 AM

Sorry I didnt get back to you sooner. I dont remember the exact use for the room fuse, but I can check my manual wiring diagrams tonight. Im guessing your 94 is different from my 93. I can also scan and post up the troubleshooting section from my 93 manual if needed, if you cant find it online.


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